Stateless Session Beans

A stateless session bean does not maintain
a conversational state with the client. When a client invokes the methods
of a stateless bean, the bean’s instance variables may contain a state
specific to that client, but only for the duration of the invocation. When
the method is finished, the client-specific state should not be retained.
Clients may, however, change the state of instance variables in pooled stateless
beans, and this state is held over to the next invocation of the pooled stateless
bean. Except during method invocation, all instances of a stateless bean are
equivalent, allowing the EJB container to assign an instance to any client.
That is, the state of a stateless session bean should apply accross all clients.

Because stateless session beans can support multiple clients, they can
offer better scalability for applications that require large numbers of clients.
Typically, an application requires fewer stateless session beans than stateful
session beans to support the same number of clients.

A stateless session bean can implement a web service, but other types
of enterprise beans cannot.